• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.377-381
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• 1998

Wear behaviors of unidirectionally oriented $Si_3N_{4w)/Si_3N_4$ composites, sintered at different temperatures with different alignments of whiskers, have been studied in parallel and perpendicular sliding directions with respect to the orientation of the whiskers by using a ball-on-disk reciprocating sliding apparatus. The results show that wear rate in parallel direction is much greater than that in perpendicular direction. With decreasing alignment of the whiskers, the wear rate decreases in parallel sliding direction and increases in perpendicular direction. With increasing sintering temperature, the wear rate increases obviously in both parallel and perpendicular directions.

• Bulletin of the Korean Chemical Society
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• v.1 no.1
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• pp.4-10
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• 1980

Simple rules for predicting nonbonded interactions have been proposed. It was found that an end-to-end nonbonded interaction is either attractive or repulsive depending on the sign of the product of AO coefficients of two end atoms in the HOMO of a closed shell conjugated system with a crowded structure. The nonbonded attraction becomes the greatest in a 4N + 2 electron conjugated system, while it is repulsive in a 4N electron system. For 4N + 1 and 4N - 1 electron systems, it is attractive but the effect is less than that in 4N + 2 system. As a result of the attractive interaction, the overlap population of an atom pair increases (decreases) if the HOMO is antibonding (bonding) for the atom pair. The rules were illustrated with some examples.

• Bulletin of the Korean Chemical Society
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• v.11 no.4
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• pp.286-290
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• 1990

The surface enhanced Raman scatterings of Zn(Ⅱ) tetrakis (4-N-methyl pyridyl) porphyrins were studied in silver sol. Zn(Ⅱ) tetrakis (4-N-methyl pyridyl) porphyrin was found to be adsorbed on silver surface via flat-on geometry with some inhomogeneous distribution in the orientation of pyridyl groups. Both the selective enhancement of Raman modes depending on the mode character and the theoretical arguments of SERS are utilized to support the above conclusion. The surface induced substitution reaction of Mn(Ⅲ) tetrakis (4-N-methyl pyridyl) porphyrin chloride to Ag(Ⅱ) tetrakis (4-N-methyl pyridyl) porphyrin was detected via surface enhanced Raman spectrum.

• Journal of the Korean Magnetics Society
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• v.15 no.4
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• pp.226-230
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• 2005

In this research, magnetic properties and annealing effects of the spin valve structures were investigated, which have Ta underlayer deposited with Ar and $N_2$ gas mixture. Also, TaN underlayer as a diffusion barrier and the substrate were investigated. The structure of the spin valve was Si($SiO_2$)/Ta(TaN)/NiFe/CoFe/Cu/CoFe/FeMn/Ta. Deposition rate was decreased and resistivity and roughness of the TaN films were increased as the $N_2$ gas flow was increased. The XRD results after high temperature annealing showed that Silicides were created in Si/Ta layer, but not in Si/TaN layer. Magnetoresistance ratio (MR) and exchange coupling field ($H_{ex}$) were decreased when the $N_2$ gas flow was increased over 4.0 sccm. The MR of the spin valves with Ta and TaN films deposited with up to 4.0 sccm of $N_2$ gas flow was increased about $0.5\%$ until the annealing temperature of up to $200^{\circ}C$ and then, decreased. TaN film deposited with 8.0 sccm of $N_2$ gas flow showed twice the adhesion of the Ta film. The above results indicate that with 3.0 sccm of $N_2$ gas flow during the Ta underlayer deposition, the magnetic properties of the spin valves are maintained, while the underlayer may be used as a diffusion barrier and the adhesion between the Si substrate and the underlayer is increased.

• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.703-708
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• 2004

The variation of the reaction pressure and reaction product during the reaction was investigated according to the total mass of the reaction mixture at the optimum composition for the preparation of u-Si3N4 powder which had been confirmed in the former investigation; 'Preparation of $\alpha$-Si$_3$N$_4$ powder in reaction system containing molten salt by SHS - part 1. synthesizing of powder'. When the total mass of the reaction mixture was 100g, the minimum pressure for a complete reaction was 60atm in 5L reactor, whereas the reaction was incomplete in the case that the mass exceeded 200g because of pressure increase. Also, as the mass of the reaction mixture increased, the reactivity linearly decreased. Hence, the complete reaction was realized by decreasing an initial $N_2$ pressure, and thus obtained minimum initial pressure was recorded 20 atm for the initial mixture of 500g. The reason of the incomplete reaction with pressure Increase was found to be that NH$_4$Cl vapour which was suppressed by the gas pressure acted as a diluent.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.4
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• pp.180-186
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• 2023

Positive bias temperature instability (PBTI) degradation of n⁺ and p⁺ poly-Si gate high-voltage(HV) SiO2 dielectric nMOSFETs was investigated. Unlike the expectation that degradation of n⁺/nMOSFET will be greater than p⁺/nMOSFET owing to the oxide electric field caused by the gate material difference, the magnitude of the PBTI degradation was greater for the p⁺/nMOSFET than for the n⁺/nMOSFET. To analyze the cause, the interface state and oxide charge were extracted for each case, respectively. Also, the carrier injection and trapping mechanism were analyzed using the carrier separation method. As a result, it has been verified that hole injection and trapping by the p⁺ poly-Si gate accelerates the degradation of p⁺/nMOSFET. The carrier injection and trapping processes of the n⁺ and p⁺ poly-Si gate high-voltage nMOSFETs in PBTI are detailed in this paper.

• Journal of Environmental Science International
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• v.12 no.4
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• pp.427-437
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• 2003

An evaluation of the application of SBR and biofilm en small sewerage system was conducted. A newly developed small sewerage system, using SBR, was successfully applied to the nutrient treatment using municipal wastewater. The system was consisted of 6 compartments. Two systems, with SBR (A type) or without SBR (B type), were compared by several parameters (COD, SS, T-N, NH$_4$$\^$+/-N, NO$_3$$\^$-/-N, NO$_2$$\^$ -/-N, alkalinity, pH, DO) in all experimental periods. Also, the time variation of several parameters (DO, pH, NH$_4$$\^$+/-N, NO$_3$$\^$-/-N NO$_2$$\^$-/-N) was examined in a SBR applied sewerage system. T-N removal efficiency of B type Was higher than that Of A type by the effect of nitrification and denitrification even though the COD removal efficiencies were similar. In aeration stage, the pH was decreased from 6.4 to 6.3 within 1 h and increased to 6.65 at the end of aerobic stage, and pH was decreased to 6.2 in non-aeration stage, and these phenomena were explained. The effects of nitrification and denitrification were compared in A type and B type sewerage system, and the typical nitrification and denitrification were observed in B type sewerage system.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.426-431
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• 2006

Acryl and vinyl sulfone functionalized blue and orange azo dyes were prepared by the coupling reaction of 6-bromo-2-cyano-4-nitroaniline and 2,5-dimethoxy-4-(vinylsulfonyl)benzenamine with 3-acrylamido-(N,N-diethylamino)benzene and 3-methyl-(N,N-diethylamino)benzene, respectively, for the coloring of poly(methyl methacrylate) (PMMA). Allyl functionalized dye was also prepared by reacting vinyl sulfone-containing dye with allylamine. Three types of dyeing method were used: the copolymerization of reactive dye with methyl methacrylate (MMA) and dyeing by polymerization of MMA in the presence of polymeric dye and dye 2 without reactive function. The color fastness for the three PMMAs were evaluated by comparing the solubility of dye under various conditions.

• Environmental Engineering Research
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• v.16 no.4
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• pp.231-236
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• 2011

Biological nitrogen removal, using a continuous flow packed-bed reactor (CPBR) in a consecutive nitrification and denitrification process, was evaluated. An apparent decline in the nitrification efficiency coincided with the steady increase in $NH_4{^+}$-N load. Sustained nitrification efficiency was found to be higher at longer empty bed contact times (EBCTs). The relationship between the rate of alkalinity consumption and $NH_4{^+}$-N utilization ratio followed zero-order reaction kinetics. The heterotrophic denitrification rate at a carbon-tonitrogen (C/N) ratio of >4 was found to be >74%. This rate was higher by a factor of 8.5 or 8.9 for $NO_3{^-}$-N/volatile solids (VS)/day or $NO_3{^-}-N/m^3$ ceramic media/day, respectively, relative to the rates measured at a C/N ratio of 1.1. Autotrophic denitrification efficiencies were 80-90%. It corresponds to an average denitrification rate of 0.96 kg $NO_3{^-}-N/m^3$ ceramic media/day and a relevant average denitrification rate of 0.28 g $NO_3{^-}$-N/g VS/day, were also obtained. Results presented here also constitute the usability of an innovative porous sulfur ceramic media. This enhanced the dissolution rate of elemental sulfur via a higher contact surface area.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.929-932
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• 2014

We explored interfacial electronic structures in indium tin oxide (ITO)/DNTPD/N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB) layer stack in an OLED to clarify the real role of an aromatic amine-based hole injection layer, DNTPD. A hole injection barrier at the ITO/DNTPD interface is lowered by 0.20 eV but a new hole barrier of 0.36 eV at the DNTPD/NPB is created. The new barrier at the DNTPD/NPB interface and its higher bulk resistance serve as hole retardation, and thus those cause the operation voltage for the ITO/DNTPD/NPB to increase. However, it improves current efficiency through balancing holes and electrons in the emitting layer.